Production of ether esters



Patented July 31, 1951 UNITED STAT PRODUCTION OF ETHER ESTERS Malcolm Kent Smith, Elizabeth, N. 1., assignor to The Baker Castor Oil Company, Jersey City, N. J., a corporation of New Jersey No Drawing. Application July 17, 1947, Serial No. 761,731

12 Claims. (Cl. 260-4105) This invention relates to improved pure ether esters and to the production of ether esters, and more particularly to the reaction of castor oil with glycol monoethers to effect the alcoholysis of the castor oil, thereby forming the ricinoleic acid esters of glycol monoethers. Such purified ether esters and their acylated derivatives have great utility as plasticizers for natural and synthetic rubber and resinous materials.

Investigations have been made heretofore on alcoholysis reactions of the general type described herein, for example, as reviewed in an article in Oil 8: Soap 21, 145-148 (1944). The investigations reviewed in that article led the writers to the conclusion that such alcoholysis reactions are incomplete. It is also suggested in the article that an advantageous method for preparing the esters of the present inventionv involves the reaction of the methyl ester of a fatty acid with an alkylene glycol monoether at elevated temperatures such as 200 C. in the presence of catalysts such as litharge, lead naphthenate, lead soaps, and various alkaline salts.

In direct contrast to the findings and predictions ofthese prior art investigations, the inventor has discovered a process for the formation of ricinoleic acid esters of glycol monoethers, in which the reactions can and do go to completion, both in the laboratory and on a commercial scale. As an example of the completeness metal hydroxides as catalysts in aprocess of the type described in the present invention gives detrimental results, in that the reaction is quite slow and yields unidentified products which are gels or solids. The process of that patent involves the use of an inert diluent and when using sodium hydroxide as catalyst, the'reactio'n is carried out at the elevated temperature of 80 2 C. For the reasons stated, the patentees preferred catalysts are the glycol alkali metal monoethers corresponding to the glycol ether being esterlfied, which requires a preliminary reaction for the formation of those catalysts.

In contrast to the teaching of the patent above referred to, the present invention performs the reaction at ordinary temperatures. eliminates the necessity for the preliminary formation of an alcoholate from a glycol ether, and avoids the production of undesirable gels. The purity of the final ricinoleic acid esters according to the present invention is considerably greater than heretofore shown to be possible, in fact the degree of esteriflcation or the esters prepared in accordance with the process of this invention is at least about 98% complete. The importance of this factor is especially emphasized by the greatly improved quality of the acylated derivatives of the ricinoleic acid esters prepared by the process of this invention when acylation reactions are performed thereon. The purified esters of this invention and their acylated derivatives are particularly eiiective as plasticizers for natural rubber. synthetic rubber and resinous materials. The reaction of the process goes to substantial completion and enables the production of the desired esters to be accomplished more economically than hitherto believed possible by previously known processes. The esters of the present invention have minimal free fatty acid content.

Other objects and advantages of the invention will be apparent from the following description.

According to the process of this invention, ricinoleic acid esters of glycol monoethers are prepared by the interaction of castor oil with a glycol monoether in the presence of an alkali metal hydroxide. It is desirable that the castor oil used in the process of this invention be substantially neutral, and, in any case, that it have a free fatty acid content of not more than about 0.5% by weight. This condition can be attained by known methods. When the oil used has a higher acid value, a larger than normal amount of alkaline catalyst must be used in order that the acid be neutralized. Even when this is done, the esteriflcation reaction is slow, resulting in a product having a high acid value and, in extreme cases, the reaction mixture tends to gel and thereby becomes diiilcult to process.

A wide variety of glycol monoethers may be utilized in carrying out the process of this invention, particularly alkylene and polyalkylene glycol monoalkyl ethers an d monoaryl ethers. Typical examples of such monoethers are 2- methoxy ethanol, 2-ethoxy ethanol, 2-butoxy ethanol, 2-phenoxy ethanol, 2-benzyloxy ethanol, the monomethyl ether of diethylene glycol, and the monobutyl ether of tetraethylene glycol.

The molar ratio of the glycol monoether to the castor oil is rather critical, and should be in the range from about 7.0 to 1 to about 12 to 1. The best results are obtained when the molar ratio is between about 8.5 to 1 and about to 1. When the reactants are present in these preferred ratios, the reaction proceeds at an optimum rate to completion.

The carrying out of the process of this invention is simplified by the fact that the reaction goes best at normal atmospheric temperatures, that is, temperatures in the range from about .20 to about 35 C. The preferred operating range is from about 25 to about 30 C. At temperatures lower than those indicated, the reaction proceeds so slowlyas to be uneconomical. Higher temperatures than those indicated cause loss of catalyst due to saponification, with deleterious amounts of soap being formed.

The preferred alkaline materials for use as catalysts are the alkali metal hydroxides, such as sodium hydroxide and potassium hydroxide. The amount of alkaline catalyst required to effeet the desired reactions is preferably from about 0.01 to about 1.0% by weight, based on the amount of castor oil used. The dry catalyst may be dissolved in the heated glycol monoether, but color develops in the latter when this is done. It is, therefore, preferable to introduce the catalyst into the reaction zone in the form of a concentrated aqueous solution, for example, a 50% solution.

The castor oil and glycol monoether charged to the reactor should be substantially anhydrous. The presence of water in the reaction zone results in higher percentages of free fatty acids in the product; for most purposes, it is desirable that the finished ester have a minimum free fatty acid content. The presence of water also slows the reaction, and, when the amount of water present exceeds about 6% by weight of the glycol monoether, the reaction is stopped.

The time required for the reaction between the glycol monoether and castor oil varies, depending upon the exact conditions used, from about 30 to about 90 minutes. The physical constants of the pure ester products of this invention can be determined, and set up as standards for determination of whether a particular reaction has gone to completion.

When the reaction is complete, the reaction mixture may be worked up in any desired manner. Thus, the excess glycol monoether may be separated from the final reaction mixture by vacuum distillation either before or after the neutralization of the catalyst with a mineral acid. The catalyst must be neutralized at some stage of the processing or the portion of the final reaction mixture containing the desired ester product may be washed countercurrently in an apparatus such as that of Colbeth U. S. Patent 2,249,746. The point at which the neutralization is efl'ected depends somewhat on the material from which the reaction vessel or stillpot, from which the excess glycol monoether is volmaterial is a copper alloy the catalyst must be neutralized before heat is applied; while when the vessel or pot is made, for example, from stainless steel, the catalyst need not be neutralized before the reaction mixture is heated. Neutralization before heating to volatilize and remove excess glycol monoether yields a finished ester with a lower free fatty acid content than if the. heating is carried out without prior neutralizatlon. In the latter case, the free fatty acid content can be lowered by washing the mixture, which has been freed from excess glycol monoether, in an apparatus such as that of the Colbeth patent referred to. This effects removal of soaps prior to the final neutralizing wash with acidified water.

The excess glycol monoether need not be separated from the reaction mixture by distillation. In any event, the final reaction product is water-washed to separate the glycerine formed in the reaction, the catalyst, and, when the distillation step is omitted, the excess glycol monoin two hours using equal weights of castor oil (having a. free fatty acid content of 0.5%) and 2-methoxyethanol, and 0.5% of sodium hydroxide, based on the weight of castor oil used. The material charged to the reactor was substantially anhydrous. The dry catalyst was added to the reactor with the methoxy ethanol, being dissolved inthe latter by warming. The color of the finished ester was somewhat affected by this procedure, as the methoxy ethanol developed a yellowwolor on being warmed with the catalyst. At the end of the two hour reaction period, the reaction mixture was washed free of excess methoxy ethanol, of glycerine formed in the reaction, of catalyst, and of any soap formed, by a batchwashing, with water. The separated ester was dried under vacuum, and had a refractive index of 1.4631 and an A viscosity (Gardner-Holdt).

Example 2.-The same ester was prepared, again using 0.5% of sodium hydroxide, based on the weight of castor oil used, dissolved in heated 2-methoxy ethanol. In this case, the reaction was run at 25-30 C. for one hour, using .233

parts by weight of castor oil (having free fatty.

acid content of 0.4%) and 143 parts of 2-methoxy ethanol. The final reaction mixture was worked up as in Example 1, yielding a good product having a refractive index of 1.4643.

Example 3.--This reaction was carried out as in Example 2, except that 200 parts by weight of castor oil were used with 147 parts by weight of 2-methoxy ethanol. The Z-methoxy ethyl ricinoleate prepared in this way had a refractive index of 1.4641.

Example 4.-300 parts by weight of substantially neutral castor oil were reacted with 220 parts by weight of Z-methoxy ethanol in the presence of 3 parts of a 50% aqueous solution of sodium hydroxide for 2' hours at 2530 C. At the end of this time, the catalyst was neutralized with dilute phosphoric acid: the excess methoxy atilized, is constructed; for example, when the 15 eth nol was distilled from the reaction mixture charged to a reactor:

under vacuum; thedistillation residue was waterwashed in an apparatus similar to that of Colbeth U. 8. Patent 2,249,746; and the separated ester was dried under vacuum. The 2-methoxy ethyl ricinoleate prepared had the following constants: refractive index: 1,4648; specific gravity 0.): 0.954; viscosity (Gardner-Holdt):

saponiflcation value: 158.8.

Example 5.-The ricinoleic acid ester of the mono methyl ether of diethylene glycol was preby dissolving 1 part by weight of dry sodium hydroxide in 309 parts of the mono-methyl reactor: 300 parts by weight of castor oil (having a free fatty acid content of 0.25%) 380 parts of 2-butoxy ethanol; 1.3 parts of a 65% aqueous solution of potassium hydroxide. The reaction was allowed to proceed for 90 minutes at a temperature of -25 C. The final reaction mixture was worked up as in Example 4. The 2-butoxy ethyl ricinoleate had a good color, and a free fatty acid content of less than 0.1%. This ester, as well as those prepared in the other examples, is a highly useful plasticizer for synthetic rubbers and resinous materials.

Example 7.-The following materials were 300 parts by weight of substantially neutral castor oil; 490 parts of 2- phenoxyethanol; 1.6 parts of a 65% aqueous solution of sodium hydroxide. This mixture was agitated for 30 minutes at a temperature of 30 C. The product was worked up as in Example 4, the 2-phenoxy ethyl ricinoleate obtained having a good color and a free fatty acid content of less than 0.1

Example 8.The following materials were charged to areaction vessel: 300 parts by weight of substantially neutral castor oil; 390 parts of 2 benzyloxy ethanol; 2.4 parts of a 50% aqueous solution of sodium hydroxide. This mixture was agitated for 75 minutes at a temperature of C. The final reaction mixture was worked up as in Example 4. The 2-benzyloxy ethyl ricinoleate obtained had a good color, and a free fatty acid content of about 0.1%

Example 9.-The following materials were charged to a reaction vessel: 300 parts by weight of substantially neutral castor oil; 310 parts of the mono-ethyl ether of diethylene glycol; 2.7 parts of a 50% aqueous solution of sodium hydroxide. This mixture was agitated for 90 minutes at a temperature of 25 C. The reaction mixture was then worked up as in Example4. The ricinoleic acid ester of the mono-ethyl ether of diethylene glycol obtained in this manner had a good color, and a free fatty acid content of less than 0.1%.

Example 10.-In a plant run, the charge to the reactor was as follows: 480 parts by weight of castor oil (having a free fatty acid content of 0.25%); 360 parts by weight of 2-methoxy ethanol; 3.35 parts by weight of a 50% aqueous solution of sodium hydroxide. This mixture was allowed to react for 90 minutes at a temperature of 25-30 C. At the end of this time, the catalyst was neutralized by the addition of 3.05 parts by weight of phosphoric acid. Following this, the

excess methoxy ethanol was distilled of! under vacuum. The distillation residue was washed and dried as in Example 4. Batches of 2-methoxy ricinoleate prepared in this way had the following constants: refractive index: 1.4635-1.4650; saponiilcation value: 158.0-1600; viscosity (Gardner-Holdt): A -A-1.

The following examples illustrate the beneficial properties conferred on synthetic rubber and resin compositions by the incorporation therein of a ricinoleic acid ester of a glycol monoether or of an acetyiated derivative of such an ester. Such acetylated and other acylated derivatives can be prepared readily and in quite pure form from any of the purified esters produced by the process of this invention. The non-acylated esters are. treated, by known procedures, with such acylating agents as acetic anhydride, butyric acid, oleyl chloride, benaoyi chloride and the like.

In the plasticization of rubber and synthetic rubbers, and of cellulose derivatives, polyvinyl acetals and related resins, there is little to choose between the acylated and non-acylated derivatives; but, in the case of vinyl halide resin compounding, the use of the acylated derivatives is mandatory, since acylation renders the esters of this invention compatible with such resins.

Example 11.--2-methoxyethyl recinoleate in GR-S rubber. GR-S rubber (butadiene-styrene copolymer of 76.5% butadiene and 23.5% styrene) was compounded in a typical tread stock formulation and vulcanized at 292 F. to optimum cure. The formulation was as follows:

Such a stock was plasticized both with 2-methoxyethyl ricinoleate and with Bardol (product a Barrett Div., Allied Chemical & Dye Corp.), the latter being a widely used coal-tar derivative which is generally accepted as being a satisfactory plasticizer for GR-S. Data illustrating the differences in physical properties between these two vulcanizates are as follows:

Bardol Aged Aged used 2 days 1 days Modulus 300 675 Tensile p. s. i l, 550 1, 075 1, 750 Elongation, per cent 565 285 185 Set, Per Cent 20 10 5 Shore Hardness 60 Per Cent Volatile C 2.1 3. 3

Z-methoxyetlryl ricinoleate Aged Aged Unaged 2 days 7 days Modulus @aoo 1,125 Tensile, p. s.'i 2, 150 1,900 1,625 Elongation, per cent. 600 315 240 Set. Per Cent l5 l0 5 Shore Hardness 50 .70 75' Per Cent Volatile 100 C 2.1 2.1,

It may be seen from these data that 2-'methoxyethyl ricinoleate is a superior plasticizer to Bardol for GR-S rubber. The softening action of the aaeaam 7 ricinoleate is initially greater than that of the Bardol, and the ricinoleate composition retains this'quality in a higher degree upon being subjected to oven-aging. The quality of the recln- 8 These test results show the z-methoxyethyl ricinoleate to the the more effective plastieizer in the unaged condition and this advantage is. maintained and improved after the vulcanizates have oleate composition is particularly shown by its been subjected to oven-aging. The value of the ability to maintain a high elongation value after 2-methoxyethyl ricinoleate is shown particularly such accelerated aging and to show ony moderate in the excellent elongation values imparted thereincrease in Shore hardness. by and the relatively ow volatility of the stock Example 12. 2-methoxyethyl ricinoleate in thus compounded when subjected to oven-aging. Hycar OR-15. As in Example 11, a tread stock 10 Example 13-- -me h yethyl acetyl ricintype of formulation was used and, in this case, oleate in VYNW. In vinyl compounding, zthe effectiveness of 2-methoxyethyl ricinoleate oxyethy aceliyl ricilloleate is c mpa ed w h dias a plasticizer was compared with the effectiveoctyl phthalate, which is generally accepted as n of tributoxy ethyl phosphate, a well known being the most satisfactory plasticizer for vinyl plasticizer for butadiene-acrylonitrile copolymers. 15 resins presently available. The data given below The formulation used was as follows: show the eil'ects of using 30 parts by weight of lasticizer with 70 parts of resin when the resin Parts b e1 ht Hycar OR 15 1 17 5 is VYNW (copolymer of about 93-95% vinyl chlo- Zinc Oxide "5 5 ride and about 57% vinyl acetate), and the plas- Carbon black 5o 20 ticizers compared are Z-methoxyethyl acetyl ricinsteam acid .::::::::::::::I:::::::::::: 0 5 oleate and di-octyl phthalate These two Accelerator (2,2'-benzothiazyl disulfide) 1.5 compositions were utnformly fiuxefi down on a sulfur 1.5 chrome-plated plastics compounding mill and P1 asticizer 20 sheets from the mill were press-polished and tested. Tests were made after oven-aging for 1 R 1-". bb btd.- lit'l poly i e r o abo ut 8 5 7: b dle 1 le -1, f 8 n ;ifi)ll 55 7 gdays at 2 C" and also after light aging for 100 acrylonitl'ile. ours at C Di-octyl phthalate Per Cent Per Cent Per Cent Low Temp. T fle E1 Plast c zer F1 o0 Plasticizer ta s? was Original n 3,395 265 -90 0.20 After oven-aging 3, 275 265 2. 1 After light-aging 2, 775 190 Z-methoryethyl acetyl ricinoleate Per Cent Per Cent Percent Pl sticizer LWTemP- Plesti' T 11 El Fl ,0. 5225 3 5 2 9 Pissed ggggggg Original 3, 380 280 After oven-aging 3, 195 280 After light-aging 2, 830 225 This formulation was cured at 307 F. for a sufli- These results show Z-methoxyethyl acetyl ricincient period of time to develop optimum cure. As in Example 11, the resulting vulcanizates were tested unaged and after being subjected to ovenaging for 2 days and 7 days at 100 C.

Tributary ethyl phosphate Un- Aged Aged aged 2 days 7 days Modulus 300% l, 575 Tensile. p. s. i. 2. 075 1, 675 2, 225 Elongation, per ccx 380 210 170 Set, per cent l0 8 5 Shore Hardncss Per cent Volatile 4. 3 8. 5

Z-methoccyethyl rzcinoleate Un- Aged Aged aged 2 ys 7 days Modulus 300% 850 1, 750 Tensile, p. s. i 2, 700 050 1, 725 Elongation, per centv 620 445 200 Set. per cent 25 15 5 Shore Hardness 60 70 75 Per cent Volatile 100 C 2. 5 3. 6

oleate to be equivalent or superior to DOP in all properties, both original and after various form of accelerated aging, except for water extraction.

Example14.-2-methoxyethyl acetyl ricinoleate in VYNS. In this case, 2-methoxyethyl acetyl ricinoleate was compared with DOP as a plasticizer for VYNS (copolymer of about 88.5-90.5% 0! vinyl chloride and about 9.511.5% vinyl acetate). Again, 30 parts by weight of plasticizer were used with 70 parts of the resin, and the compositions were fluxed down on a plastics mill. The flexible films thus resulting were formed into smooth films in a press and tested in the unaged condition, also after being heated-aged for 4 hours at C. and again after being light-aged at 45 C. for 100 hours. The data are tabulated below in three consecutive sections representing these changes in the aged condition of the film: Un-

75 aged, Over-aged, Light-aged.

' I Per Cent Low Tern Modulus Per Cent Shore P 100 0. Elongation Hardness fitfi ja {33, 3

UNA GED Ricinolccte 1, 265 2, 445 270 85 -50 DOP 1, 580 2, 685 250 95 50 OVEN -A GED Bicinoleate 985 1, 245 65 1. 32 -40 D01 1, 210 I 990 235 65 2. 76 40 L1 GHT-A GED Ricinoleate 965 2, 360 300 85 168 DOP l, 175 l, 875 215 88 226 These results show 2-methoxyethyl acetyl ricinoleate to be equivalent to DOP as a plasticizer for VYNS.

In view of the many changes and modifications that may be made without departing from the principles underlying the invention, reference should be made to the appended claims for an understanding of the scope of the protection atforded the invention.

\ What is claimed is:

1. The process for the production of the ricinoleic acid ester of a glycol monoether selected from the group consisting of alkylene and polyalkylene glycol monoalkyl ethers and monoaryl ethers, which comprises reacting said monoether with castor oil containing not more than 0.5% of free fatty acids, said reactants being utilized in a molar ratio of from '7 to 1 up to 13 to 1 respectively, under substantially anhydrous conditions at a temperature in the range from to 35 C. and in the presence of from 0.01% to 1.0% of alkali metal hydroxide, based on the weight of castor oil used.

2. The process of claim 1, in which said monoether is an alkylene glycol monoalkyl ether.

3. The process of claim 1, in which said monoether is Z-methoxy ethanol.

4. The process of claim 1, in which said monoether is an alkylene glycol monoaryl ether.

5. The process or claim 1, in which said monoether is 2-benzyloxy ethanol.

6. The process of claim 1, in which said monoether is a polyalkylene glycol monoalkyl ether.

7. The process of claim 1, in which said mono ether is the monomethyl ether of diethylene glycol.

8. The process of claim 1, in which said molar ratio is in the range from 8.5 to 1 up to 10 to 1.

9. The process of claim 1, in which the reaction temperature is in the range from 25 to 30 C.

10. The process of claim 1, in which said alkali metal hydroxide is sodium hydroxide.

11. The process of claim 1, in which said alkali metal hydroxide is charged to the reactor in the form of a concentrated aqueous solution.

12. The process of claim 1, in which the unneutralized reaction product is freed from glycerine, monoether, alkali metal hydroxide, and any soap present by water-washing, and the resulting purified ricinoleic acid ester is dried.

MALCOLM KENT SMITH.

REFERENCES CITED The following references are of record in the tile of this patent:

UNITED STATES PATENTS Number Name Date 1,739,315 Kessler et a] Dec. 10, 1929 2,285,420 Doolittle June 9, 1942 2,310,395 Carruthers Feb. 9, 1943 2,386,182 Balcar Oct. 9, 1945 OTHER REFERENCES "Ether esters, plasticizers for vinyl coating": Tuttle et al., Modern Plastics, December 1946 (pages 163-166) 

1. THE PROCESS FOR THE PRODUCTION OF THE RICINOLEIC ACID ESTER OF A GLYCOL MONOETHER SELECTED FOR THE GROUP CONSISTING OF ALKYLENE AND POLALKYLENE GLYCOL MONOALKYL ETHERS AND MONOARYL ETHERS, WHICH COMPRISES REACTING SAID MONOETHER WITH CASTOR OIL CONTAINING NOT MORE THAN 0.5% OF FREE FATTY ACIDS, SAID REACTANTS BEING UTILIZED IN A MOLAR RATIO OF FROM 7 TO 1 UP TO 13 TO 1 RESPECTIVELY, UNDER SUBSTANTIALLY ANHYDROUS CONDITIONS AT A TEMPERATURE IN THE RANGE FROM 20* TO 35* C. AND IN THE PRESENCE OF FROM 0.01% TO 1.0% OF ALKALI METAL HYDROXIDE, BASED ON THE WEIGHT OF CASTOR OIL USED. 